Conventional oil-in-water or water-in-oil emulsions, particularly those used for topically applied cosmetics and pharmaceuticals and agricultural sprays, are prepared with considerable heating and high-shear mixing, and generally require a multiplicity of ingredients to ensure suitable emulsification.
Additionally, these formulations may contain a myriad of other ingredients in order to achieve a useful balance of emulsification, viscosity, and stability. Also, the production of satisfactory emulsions is energy intensive, entailing the use of high shear for mixing the phases and prolonged exposure to elevated temperatures.
Commonly known emulsions, particularly those comprising skin creams and lotions, are formulated with at least one and not atypically several emulsifiers which assist in the formation of the oil-in-water or water-in-oil emulsions. Typical emulsifiers comprise a variety of synthetic chemicals, including laureth-4, steareth-10 and PEG-5 lauramide. The use of such synthetic emulsifiers, particularly for topical skin applications, raises the specter of consumer safety concerns such as potential skin irritation and sensitization via exposure to synthetic or biologically non-compatible agents.
Certain animal proteins, usually hydrolyzed, are used in small concentrations as substantive coatings for skin and hair. These materials are solubilized, as opposed to having colloidal properties, and problems with viscosity, stickiness, and odor limit their concentration in a formulation and limit their service as useful emulsifiers. However, these materials are not recognized as having the ability to form useful emulsions for topical application of active ingredients. Moreover, because these animal proteins have been chemically hydrolyzed, they are not naturally occurring and carry some risk of skin irritation.
In addition, oils and/or oily substances are common constituents in topical skin applications, specifically cosmetic creams and lotions. These oils and/or oily substances are desirable additions to such topical applications in that they tend to form a thin, fluid film which retards the drying of the skin after evaporation of other volatile ingredients found in the cream or lotion. However, it is also desirable to reduce the greasy or oily feel of these creams and lotions on the skin. In order to achieve a non-oily skin feel, the resulting film should be either very thin or contain very little oil.
Thus, presently known lotion and cream formulations generally comprise oil-in-water emulsions and/or are preferably applied to the skin in a very thin film. In either case, the resultant film is not efficient as an occlusive film for preventing moisture loss from the skin and may still contain an undesirable amount of oil. Also, such films are easily rubbed off, thus allowing dehydration of the skin and a resultant uneven application of active ingredients contained therein.
Other attempts documented in the prior art to improve the film characteristics of such topical skin applications include the addition of synthetic film-forming polymers to the skin lotion or cream. In practice, the concentration of the polymer in the formulation is usually quite low, on the order of only a few percent, in order to avoid the undesirable aesthetics of a polymeric coating on the skin. Additionally, higher polymer concentrations generally result in formulation viscosities which are too high for practical use.
However, the use of low concentrations of polymer also limits the amount of oil which can be bound into the film, thereby limiting the effectiveness of the film as a moisture entrapper over the skin and/or carrier of active ingredients. Moreover, the addition of synthetic polymers to a topical lotion is less desirable from a consumer standpoint in terms of safety concerns.
The present invention overcomes all of the above objections by utilizing natural proteinaceous materials which not only act as emulsifiers to emulsify a lipophilic phase with an aqueous phase, but also produce resultant thin films. These films may preferably have non-oily, dry, flexible, occlusive, invisible and/or substantive properties, and can form films on surfaces such as skin, hair, and other surfaces such as plant leaves and other vegetation. It has been found that virtually any lipophilic constituent, including oils or oily substances, can be readily emulsified with these proteinaceous materials. These phases include emollients, oil-based vitamins, defoliants, essential oils, flavorants, sunscreen agents, insect repellents, pharmaceuticals and the like along with other active ingredients which are soluble or can be carried in the lipophilic phase. Additionally or alternatively, similar active ingredients can comprise the aqueous phase of the emulsion of the present invention.
Another surprising aspect of this invention is that the emulsions can be formed spontaneously at room temperature and with minimal agitation. Also, the proteinaceous emulsifiers of the invention are totally natural and are extremely safe to use.
The emulsions of the present invention are typically off-white, smooth, creamy, and may preferably dry quickly when applied as a thin film to a surface. Also, since the proteinaceous materials of the invention serve in a multiple capacity as emulsifiers, co-emulsifiers, thickeners, whiteners and film-formers, a minimal number of ingredients is required to build a useful formulation.